A clamshell mobile or handheld communication device generally has a base and a hinged or sliding lid that can be closed over the base. Such devices generally provide a user with a primary display inside the lid or on the base that is visible when the device is open and provides the user with a user interface. Furthermore, some clamshell devices have a secondary display on the outside of the lid that is visible when the device is closed and provides the user with a secondary user interface.
The device may be provided with navigation tools or buttons on the base or inside the lid that may be accessed when the device is opened. Such buttons may include a keypad, a scroll wheel, a trackball, or other similar mechanisms. These buttons are enclosed within the device when the device is closed. As such, it is often necessary to provide buttons that do not protrude from the base, to avoid the buttons being compressed between the halves of the device, which may damage the buttons and/or the display immediately upon compression or over time. Alternatively, the lid and/or base may be designed with space, such as a depression, to accommodate any protruding buttons when the device is closed. It may also be necessary to provide additional navigation buttons on the exterior of the device, so as to be accessible when the device is closed, for the purpose of navigating a user interface on the secondary display.
It is often desirable to provide a handheld device that has as slim a profile as possible, to make it light and portable as well as aesthetically pleasing. However, this becomes a challenge for clamshell devices since there is less space to accommodate the buttons, whether protruding or non-protruding, on the base when the device is closed. This is one barrier to providing trackball, joystick or rocker style navigation buttons in a clamshell device. Such buttons typically protrude at least a few millimeters from the base in order to be accessible and used by a user's finger. As explained above, this would result in the button pressing against the inside of the lid when the device is closed, which may damage the display and/or the button.
A solution would be to provide a depression on the inside of the lid to accommodate such protruding buttons when the device is closed. However, this necessarily increases the thickness of the device. The trend is typically towards thinner devices, some perhaps as little as 10 mm thick when closed. Since a protruding button may need to protrude as much as 2 mm, providing a depression to accommodate such a button takes up a significant amount of space on a thin device and significantly limits how thin the device may be.
Another solution is to provide the button in a flush mount. That is, the button is provided in a depression on the base of the device. However, in order to maintain the thinness of the device, such a flush mount may be very shallow and wide, taking up a large amount of the limited space on the base of the device, and making the button difficult to access by a user's finger, particularly if the user has a large fingertip that might not fit in the depression, and detracting from the usability of the button. Further, the presence of a depression also presents mechanical limitations in the design and layout of the device and its circuitry. Space for circuitry in a handheld device is very limited, and typically it is desirable to maximize useable circuitry space within the device as much as possible. In a clamshell device, the spaces within both the lid and the base are typically almost entirely filled with circuitry. The presence of a depression for accommodating a protruding button takes up significant space, limiting the amount and the type of circuitry that may fit within the device underneath the depression. For example, only flat components may be used in the space immediately below such a depression.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.